Nuclear facilities are required in the U.S. to monitor the effectiveness of maintenance at nuclear power plants. In 1991, the U.S. Nuclear Regulatory Commission (NRC) published the maintenance rule (MRule) as Section 50.65, “Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants,” of 10 CFR Part 50, “Domestic Licensing of Production and Utilization Facilities.” The NRC's determination that a maintenance rule was needed arose from the conclusion that proper maintenance is essential to plant safety. As discussed in the regulatory analysis for this rule, there is a clear link between effective maintenance and safety as it relates to such factors as the number of transients and challenges to safety systems and the associated need for operability, availability, and reliability of safety equipment. In addition, good maintenance is also important in providing assurance those failures of other than safety-related structures, systems, and components (SSCs) that could initiate or adversely affect a transient or accident are minimized. Minimizing challenges to safety systems is consistent with the NRC's defense-in-depth philosophy. Maintenance is also important to ensure that design assumptions and margins in the original design basis are maintained and are not unacceptably degraded. Therefore, nuclear power plant maintenance is clearly important in protecting public health and safety.
Regulatory guide 1.160 of the MRule provides that examples of SSCs that should be considered include communications and emergency lighting systems, which are necessary to successfully mitigate accidents and transients and to use the emergency operating procedures (EOPs), although they may not directly address the accident or transient, or not be explicitly mentioned in the EOPs.
Appendix R to Part 50—Fire Protection Program for Nuclear Power Facilities Operating Prior to Jan. 1, 1979 requires that “emergency lighting units with at least an 8-hour battery power supply shall be provided in all areas needed for operation of safe shutdown equipment and in access and egress routes thereto. ”The general purpose of emergency lighting systems is to provide sufficient lighting of desired quality in all areas of a station, indoors and outdoors, for normal, essential, and emergency conditions. AC station lighting is the normal lighting system used throughout a facility. Generally, normal AC lighting cabinets are energized from the non-ESF (Engineered Safety Features) 480-volt motor control centers.
AC emergency (or standby) station lighting is provided for station operation during a loss of normal AC auxiliary power. It is limited to the lighting required for the control and maintenance of ESF equipment (such as the ESF switchgear, emergency cooling equipment, control equipment, etc.) and for the access routes to this equipment. Generally, it is energized from the 480-Volt ESF motor control centers and thus receives power from the diesel generators when, and if, the sources of normal AC auxiliary power fail. Control room emergency lighting systems are similar to normal lighting systems except that the source of AC power is supplied from the engineered safety features power distribution system. These lights are normally in service at all times.
8-hour balance of plant (BOP) and safe shutdown battery emergency lighting units are provided in various locations in sufficient quantity to provide supplemental lighting for maintenance and supervision of both BOP and safe shutdown equipment. The battery emergency lighting system in the control room consists of battery operated lighting units located strategically within the control room. The units are normally de-energized and operated automatically upon failure of the ESF or non-ESF AC lighting systems.
Current emergency lighting systems are generally comprised of wet-cell batteries and incandescent lights. These systems require periodic maintenance and generally degrade over time. In some instances, these lighting systems are not capable of providing the desired eight hours of emergency lighting.
Therefore, systems and methods that overcome challenges found in the art, some of which are described above, are desired.